As eosinophils are the densest and lowest abundant leukocytes, their isolation is cost-and labor intense. This sets restrictions on many aspects of eosinophilic research. Eosinophilic cell lines are available for use; however they are not characterized in much detail, yet. Cells of the HL-60 clone 15 cell line were differentiated into eosinophilic cells with sodium butyrate with or without IL-5 cells and compared to primary eosinophils and neutrophils.